1. Field of the Invention
The present invention relates to a process for removing ethers and polycyclic aromatic hydrocarbons from water containing them, such as groundwater.
2. Discussion of the Background
Little is known on groundwater treatment. Increasingly alarming news items continue to appear regarding the contamination of groundwater and drinking water sources with organic constituents, particularly with chlorinated solvents.
A number of methods are known, however, for cleaning up waste water or industrial process water. However, this involves the reduction of pollutant concentrations which are higher by orders of magnitude compared to groundwater and drinking water requirements. The aim of these processes is to discharge water in an environmentally compatible manner or re-use the water or an aqueous solution. There is no intention of providing drinking water by such treatments.
In "Neuere Verfahrenstechnologien in der Abwasserreinigung, Abwasser-und Gewasserhygiene" [Recent Processing Technologies in Waste Water Treatment, and Waste Water and Natural Water Sanitation], R. Oldenbourg Verlag, Munich, Vienna 1984, pages 235 to 251 describe several methods for treating chlorinated hydrocarbon-containing waste water from chlorination plants. According to one process, the waste water is first made alkaline (pH 11). The subsequent stripping, which is performed by countercurrent injection of steam, gives a distillate which, after condensing, divides into a chlorinated hydrocarbon phase and an aqueous phase. At the bottom of the stripper (oxistripper), waste water is produced which is subsequently biologically purified.
In special cases, waste water having a pH of 1 to 2 can also be subjected to stripping with steam in countercurrent. At the bottom of the stripper, a water having a high iron and hydrochloric acid content is produced, which is fed for further treatment to a chemical and mechanical sewage treatment plant.
Chlorinated-hydrocarbon-containing mining waste water is conventionally cleaned up in an adsorber resin plant. In this case the mining waste water, after it has been freed from solids as painstakingly as possible, is passed through an adsorber resin based on a divinylbenzene/styrene copolymer. The resin can later be reactivated by steam desorption. With this process, a considerable decrease in activity was found after one year of operation, due to irreversible iron deposits. Thus, a new plant requires operation at pH 1.5.
According to Technische Mitteilungen 77 (1984), 525-526, styrene copolymers or polyacrylates are suitable for removing aliphatic and aromatic hydrocarbons, chlorinated hydrocarbons, phenols, pesticides and surfactants from waste waters. The resins are then regenerated with steam. However, in the case of pesticides, the resins are regenerated using solvents, such as acetone or methanol, or with inorganic chemicals.
In DD 249 190, hydrochloric acid, which originates from chlorination processes and is contaminated with organic substances, is purified using hydrophilic, post-crosslinked divinylbenzene/styrene copolymers which preferably have an internal surface area of 1000 to 1600 m.sup.2 /g. The resin is regenerated with steam at 130.degree. C. The bound organic substances can also be desorbed by solvents, such as alcohols and ketones.
By means of the cleanup processes cited, concentrations of &lt;0.1 mg/l are achieved with respect to individual pollutant components. However, the total amount of organic constituents or chlorinated hydrocarbons after the cleanup is at best in the range of several mg/l (or several ppm), still considerably too high for the water to be added back into flowing surface water or for use in preparation of drinking water.